When every Iterable record in a pipeline fails, check the toplevel email mapping first, not the field values. Email buried inside dataFields does not identify the contact; the toplevel email or userId must be mapped explicitly. Also trim custom email fields: a trailing space is rejected with an error that hides the real cause.

Context: The Digioh help documentation for Iterable pipelines (updated June 2026) names the most common total-failure cause: Iterable identifies contacts with a toplevel email or userId that must be explicitly mapped. A pipeline that sends the email only inside dataFields, with a blank toplevel identifier, fails on every single submission. It also notes a trailing space in a custom email field gets rejected, and the log error does not make the cause obvious.